This invention relates to a stereo image control circuit. More particularly, this invention relates to a stereo image control circuit which varies the stereo image of an audio program by widening the stereo base in a two-channel audio system. Still more particularly, this invention relates to a circuit which provides flexibility in stereo imaging by controlling a base between both channels of a stereo audio program by smoothly changing the stereo base from a "0" mono-mode via a "stereo" mode to a larger dimension, providing a deeper and more spacious imaging effect.
In the prior art, most of the existing stereo imaging circuits address partly the problem of changing the stereo base either from a MONO mode to a STEREO mode or from a STEREO mode to a WIDE mode. Such circuits are used in portable audio products and some professional effect units. For example, in AMEK's BCIII unit, a stereo image control is provided with associated circuity to vary the stereo image width from normal stereo through mono to left/right reversed stereo. In Neve's MATS (monitoring and talkback system), a stereo width control is provided with a switch so that one of the stereo auxiliary busses becomes a stereo mix bus for a second line input. A unit from Solid State Logic SL5000 M Series includes a stereo programming panel for such width control.
However, such circuits were not entirely satisfactory because of a lack of flexibility in stereo imaging over the entire range and a desire to control the stereo base between both channels of the stereo audio program. It continued to be desirable to change the stereo base of such a circuit smoothly from a MONO mode via a STEREO mode to a larger dimension, thus providing a deeper and more spacious imaging effect because of an enhanced range. In addition, it is desired to implement the circuit in a way which provides larger control of the stereo image while determining the exact, necessary amount of control without affecting the gain.
These and other aims and objectives of the invention will become apparent from a review of the written description of the invention which follows taken in conjunction with the accompanying drawings.